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I am thinking about using mostly ADA Amazonia over a thin layer of peat granules and pool filter sand in some unplanted sections for the substrate. Lighting will be supplied by ~30W of high intensity LEDs. I have a lot of huge uncertainties about other aspects of this setup. For example:

1. In addition to the Eheim Liberty HOB filter I plan to use, do I need additional sources of (lateral) water movement like a powerhead? if so, how powerful?

2. Should I inject CO2? Initial reading suggests that it will be very beneficial though I wonder about the potential pH swings of CO2 injection in very soft water.

3. What are "ideal" water parameters for these plants (pH and TDS, in particular)? I have an RO/DI filter so I can go as low as I need to.

4. Any recommended fertilization regime?

I don't have much experience with these soft-water plants so I would love to get any thoughts, ideas and feedback about any and all aspects of this setup, including the plant and substrate selection. Thank you!

No your plants don't need CO2, it will cause the pH to drop to very low levels in water without much carbonate buffering (dKH), but that isn't really a problem for plants or fish. I would add a floating plant (Pistia, Salvinia or Limnobium), and Ceratopteris (at least <"one species is a Amazonian native">).

I don't have much experience with these soft-water plants so I would love to get any thoughts, ideas and feedback about any and all aspects of this setup, including the plant and substrate selection. Thank you!

I wouldn't use ADA amazonia, it is loaded with nutrients, and has an initial ammonia spike. You could just use sand (and peat), but another "active substrate" (any of the ones they sell for Shrimps) would be OK.

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Thank you so much for your detailed answers. When it comes to plants, there is probably no one I respect more on these and other aquatics forums.

I am curious as to why so many sites, including aquaticplantscentral, flowgrow.de, plantsalive.co.uk make it sound as if CO2 injection and a nutrient rich substrate are practically required for Red Cabomba and Tonina to thrive. A few people also commented that they were only able to grow Tonina in ADA Amazonia soil, partly because of its nutrients and partly because it quite acidic. There are also a lot of comments from people saying these plants require an acidic substrate. Just out of curiosity, are you against using Amazonia only because of the initial ammonia spike? I ask because I have a lot of leftover Amazonia from my "high-tech" planted tank days and do not plan to keep any fish in this tank for a while. The filter is also already well-established.

Lastly, would you be able to give a more specific recommendation than "under 100" for TDS? If I use 100% RO/DI water the TDS with dissolved organics from peat and leaves will probably put it at 20 or so. So I can probably go anywhere in that range between 20 and 100.

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......make it sound as if CO2 injection and a nutrient rich substrate are practically required for Red Cabomba and Tonina to thrive. A few people also commented that they were only able to grow Tonina in ADA Amazonia soil, partly because of its nutrients and partly because it quite acidic........Just out of curiosity, are you against using Amazonia only because of the initial ammonia spike? I ask because I have a lot of leftover Amazonia from my "high-tech" planted tank days and do not plan to keep any fish in this tank for a while. The filter is also already well-established.

No problem with using the Amazonia, it may not soften the water if it has been used, due to the ion exchange sites already being filled with Ca++ ions etc.

I think Cabomba furcata, and particularly Tonina fluviatilis & Syngonanthus manaus, are very difficult to grow, but they are naturally aquatic plants from extremely nutrient poor and acidic environments, so there has to be more to it than just CO2 and nutrients. My suspicion is that if you have an acidic substrate and low dKH water then light is the really important parameter.

Aquascapers are only going to use high light intensity with nutrients and CO2, therefore the plants "need" lots of nutrients and additional CO2.

Lastly, would you be able to give a more specific recommendation than "under 100" for TDS? If I use 100% RO/DI water the TDS with dissolved organics from peat and leaves will probably put it at 20 or so. So I can probably go anywhere in that range between 20 and 100.

Well-Known Member

Water with a very low mineral content is a physiologically challenging habitat for plants to grow in. The ones that live there have evolved to survive in those conditions, but it's not necessarily the conditions they actually need, nor the conditions they could grow best in. Keeping it toward the higher end of the 20 to 100 uS range would probably be safer for the plants, while still being low enough for breeding blackwater Apistos.

Active Member

I think Cabomba furcata, and particularly Tonina fluviatilis & Syngonanthus manaus, are very difficult to grow, but they are naturally aquatic plants from extremely nutrient poor and acidic environments, so there has to be more to it than just CO2 and nutrients. My suspicion is that if you have an acidic substrate and low dKH water then light is the really important parameter.

Darrel, you make a very strong, logical point and others have also mentioned that providing sufficiently strong lighting is the most significant barrier to success with these plants. It does seem to put the concept of limiting growth factors on its head a bit though, doesn't it? Perhaps there is something about these plants that prevents them from absorbing much of the available light? Then again, my knowledge of plant physiology and biochemistry is very, very limited, so I could be totally off.

Water with a very low mineral content is a physiologically challenging habitat for plants to grow in. The ones that live there have evolved to survive in those conditions, but it's not necessarily the conditions they actually need, nor the conditions they could grow best in.

This is also a very good point Gerald. For example, human beings are capable of surviving in very harsh, cold environments, but those are not ideal conditions for us. On the flipside, I know that many carnivorous plants *require* very low nutrient, acidic conditions in order to survive. I think the trick is distinguishing what conditions certain species have evolved to 'tolerate' and what conditions they actually need.

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Perhaps there is something about these plants that prevents them from absorbing much of the available light? Then again, my knowledge of plant physiology and biochemistry is very, very limited, so I could be totally off.

Light drives photosynthesis, but the plant must be able to dissipate any "spare" light energy (and heat), the reason for this goes back to Newton's laws and the conservation of energy.

Aquatic plants are often CO2 limited, which means that light excess light can't be be used for photosynthesis. If you add CO2 at ~30ppm (compared to ~1ppm naturally) plants can utilise more of the available light. If CO2 isn't limiting, then almost certainly another mineral element will be, normally either nitrogen (N) or potassium (K) via Liebig's law of the minimum.

Plants that naturally grow in deep shade (Bolbitis heudelotii, Anubias barteri) have high levels of chlorophyll and are very dark green, this is to allow them to harvest every last photon of light. If you move them into regions of higher PAR then the extra photons of light harvested can't be utilised in photosynthesis and cause damage to the plant, which is why you get chlorosis and leaf burn etc.

A plant exposed to tropical sun-light is receiving a huge amount of light energy every day, equivalent to what temperate regions get at the summer solstice (but only over 12 hours, rather than 16 etc.)

This is the reason that if you have a continental climate you can grow Ludwigia sedoides, Nymphaea capensis, Eichornia crassipes etc outside during the summer, but they are very difficult to overwinter even under "intense" artificial lighting.

Active Member

Darrel, thank you for the wonderful scientific explanation. It seems to reinforce my earlier notion of putting the "limiting factor" concept on its head regarding these plants. It doesn't make sense that they'd need high light in poor nutrient/CO2 environment. There is no way for the plants to "dissipate" that energy. Perhaps the substrate in which these plants grow in the wild is very nutrient rich? That would explain why some people claim they can only grow cabomba/tonina, etc. in ADA aquasoil.

I don't know. I think if you have water with even a minimum amount of nutrients and light you will get aquatic plants grow. As a general rule, ecologically speaking, in low nutrient, high light situations you get relatively low biomass, but very high plant biodiversity, often with insectivorous plants etc.

I'm sure they grow better with more nutrients, and micro-element availability would be high in soft-water, but I think these would be what we would regard as low nutrient situations. It may be an organic carbon source is advantageous in the substrate, you could add leaf mould or peat?